Radiosensitivity and transgenerational effects in non-human species

The ALLIANCE working group on effects of ionising radiation on wildlife brings together European researchers to work on the topics of radiosensitivity and transgenerational effects in non-human biota. Differences in radiation sensitivity across species and phyla are poorly understood, but have important implications for understanding the overall effects of radiation and for radiation protection; for example, sensitive species may require special attention in monitoring and radiation protection, and differences in sensitivity between species also lead to overall effects at higher levels (community, ecosystem), since interactions between species can be altered. Hence, understanding the mechanisms of interspecies radiation sensitivity differences may help to clarify mechanisms underpinning intraspecies variation. Differences in sensitivity may only be revealed when organisms are exposed to ionising radiation over several generations. This issue of potential long-term or hereditary effects for both humans and wildlife exposed to low doses of ionising radiation is a major concern. Animal and plant studies suggest that gamma irradiation can lead to observable effects in the F1 generation that are not attributable to inheritance of a rare stable DNA mutation. Several studies have provided evidence of an increase in genomic instability detected in germ or somatic cells of F1 organisms from exposed F0 organisms. This can lead to induced radiosensitivity, and can result in phenotypic effects or lead to reproductive effects and teratogenesis. In particular, studies have been conducted to understand the possible role of epigenetic modifications, such as DNA methylation, histone modifications, or expression of non-coding RNAs in radiosensitivity, as well as in adaptation effects. As such, research using biological models in which the relative contribution of genetic and epigenetic processes can be elucidated is highly valuable.

Action-oriented community diagnosis: a health education tool

Health education research and practice have found individuals' health decisions and behaviors to be related to their perceptions of need. It has also been found that physical, social, and political conditions generated by one's community can exert important influences on individuals' ability to act on the basis of need. It appears that conducting a needs assessment is a necessary component of program planning, but the information is not sufficient for designing sustainable interventions. An Action-Oriented Community Diagnosis procedure has been developed over several years to: 1) identify normative and comparative needs determined by service agencies as well as expressed and perceived needs experienced by clients; 2) assess community conditions contributing to collective competence as well as the barriers and gaps contributing to disease and illness; and 3) increase collective competence of communities and agencies to collaborate in defining problems and needs. One of the many health education projects that have conducted such a diagnosis has been selected to illustrate the features of the procedure, the rationale behind the methods and sequence of steps, how the methods can be operationalized, and the outcomes.

[Hospital infection control--beyond the hospital]

Health care related infections are expensive untoward events, not only in terms of morbidity and mortality, but also cost. Prevention is essential, as well as limiting dissemination. Specify measures refer usually to hospital hygiene. However, health care tend to be provided more and more outside of the acute care hospital, with increasing complexity and thus risk for health care related infections. This risk varies according to patient's characteristics as well as environmental parameters. Consequently, it is essential to adapt preventive measures to situations such as home health care or nursing homes. We describe a model of regional organization for infection control in various health care settings.

What is community? An evidence-based definition for participatory public health

Increased emphasis on community collaboration indicates the need for consensus regarding the definition of community within public health. This study examined whether members of diverse US communities described community in similar ways. To identify strategies to support community collaboration in HIV vaccine trials, qualitative interviews were conducted with 25 African Americans in Durham, NC; 26 gay men in San Francisco, Calif; 25 injection drug users in Philadelphia, Pa; and 42 HIV vaccine researchers across the United States. Verbatim responses to the question "What does the word community mean to you?" were analyzed. Cluster analysis was used to identify similarities in the way community was described. A common definition of community emerged as a group of people with diverse characteristics who are linked by social ties, share common perspectives, and engage in joint action in geographical locations or settings. The participants differed in the emphasis they placed on particular elements of the definition. Community was defined similarly but experienced differently by people with diverse backgrounds. These results parallel similar social science findings and confirm the viability of a common definition for participatory public health.

Formation of furfurylthiol exhibiting a strong coffee aroma during oak barrel fermentation from furfural released by toasted staves

Furfurylthiol (FFT) is formed in white wines during alcoholic fermentation in the barrel from the furfural released by toasted staves. The quantity of furfural released into the must has a decisive effect on the quantity of FFT in the finished wine. Wines fermented in new barrels thus contain larger quantities of FFT than those fermented in used barrels. Fermentation conditions favorable to an excess production of H(2)S (hydrogen sulfide) by the yeast promote the formation of this volatile thiol. The presence of this volatile thiol in white wines is, therefore, closely related to the yeast's sulfur metabolism.

A powerful aromatic volatile thiol, 2-furanmethanethiol, exhibiting roast coffee aroma in wines made from several Vitis vinifera grape varieties

The chemical compound 2-furanmethanethiol (2FM), with a strong roast coffee aroma, has been identified in sweet white wines made from the Petit manseng grape variety, and in certain red Bordeaux wines (made from the Merlot, Cabernet franc, and Cabernet sauvignon grape varieties). This was done by extracting specific volatile thiols using p-hydroxymercuribenzoate. The 2FM has also been found in toasted oak used in barrel-making. All the Petit manseng sweet white wines and some of the red Bordeaux wines analyzed contained between a few ng/L and several dozen ng/L of 2FM. Taking into account its very low perception threshold (0.4 ng/L in a model hydro alcoholic environment), 2FM could therefore contribute to the roast coffee aroma of certain wines.

Potent and selective non-peptidic inhibitors of endothelin-converting enzyme-1 with sustained duration of action

Potent and selective non-peptidic inhibitors of human endothelin-converting enzyme-1 (ECE-1) have been designed as potential modulators of endothelin (ET-1) production in vivo. Because of its unique structural characteristics and long duration of action in vivo, the dual ECE-1 and neutral endopeptidase 24.11 (NEP) inhibitor, CGS 26303, was selected as an attractive lead for further optimization of potency and selectivity. Replacement of the P(1)' biphenyl substituent of CGS 26303 by a conformationally restricted 3-dibenzofuranyl group led to more potent and more selective ECE-1 inhibitors, such as the tetrazole 27. The remarkable effect of this P(1)' modification allowed for the first time phosphonomethylcarboxylic acids, such as 29, to display both potent (IC(50) = 22 nM) and selective (104-fold vs NEP) ECE-1 inhibition. Chemoenzymatic syntheses of the new alpha-amino acid (S)-3-dibenzofuran-3-ylalanine intermediate were developed, and improved procedures to generate substituted alpha-aminoalkylphosphonic acids were devised to support the production of various analogues. Although additional gains in intrinsic ECE-1 inhibitory potency could occasionally be achieved by addition of a P(1) side chain, these compounds (e.g. 43a) showed poor functional activity in vivo in the big ET-1 pressor test. Phosphonoalkyl dipeptides featuring 3-dibenzofuranyl groups in both the P(1)' and P(2)' positions were also very potent ECE-1 inhibitors, albeit lacking the desired selectivity against NEP. Functionally, 27and 29 were the two most efficacious compounds from this study, producing sustained inhibition of ECE-1 activity in rats, as measured by their ability to block the hypertensive effects induced by big ET-1. This profile was similar to that of a potent ET(A)/ET(B) dual receptor antagonist, SB 209670. Due to their favorable in vitro and in vivo profiles, 27 (CGS 34043) and 29 (CGS 35066) constitute new pharmacological tools useful in assessing the role of ECE-1 in pathological conditions.

Level of ICAM-1 surface expression on virus producer cells influences both the amount of virion-bound host ICAM-1 and human immunodeficiency virus type 1 infectivity

Using virions harvested from 293T cells stably expressing either low or high levels of surface ICAM-1, we determined that the number of virus-embedded host ICAM-1 proteins is positively influenced by the expression level of ICAM-1 on virus producer cells. Moreover, the increase in virion-bound host cell membrane ICAM-1 led to a concomitant enhancement of virus infectivity when a T-cell-tropic strain of human immunodeficiency virus type 1 (HIV-1) was used. The phenomenon was also seen when primary human cells were infected with virions pseudotyped with the envelope protein from a macrophage-tropic HIV-1 isolate, thus ruling out any envelope-specific effect. We also observed that target cells treated with NKI-L16, an anti-LFA-1 antibody known to increase the affinity of LFA-1 for ICAM-1, were markedly more susceptible to infection with HIV-1 particles bearing on their surfaces large numbers of host-derived ICAM-1 proteins. Given that cellular activation of leukocytes is known to modify the conformational state of LFA-1 and induce ICAM-1 surface expression, it is tempting to speculate that activation of virus-infected cells will lead to the production of HIV-1 particles bearing more host ICAM-1 on their surfaces and that such progeny virions will preferentially infect and replicate more efficiently in activated cells which are prevalent in lymphoid organs.

Response latencies for false memories: gist-based processes in normal aging

Three experiments have demonstrated that age-related increases in both probability and speed of false recognitions for word lists depended on the use of a gist-based memory strategy. When test conditions promoted a gist strategy, both younger and older participants were as likely to falsely recognize a thematically associated lure as to correctly recognize a studied item, and both groups were equally fast in making these decisions. However, when test conditions deemphasized a gist-based strategy, older adults were more likely than younger adults, and faster, to falsely recognize both strong and weakly associated lures. These findings suggest an age-related increase in reliance on gist-based processing that may underlie age differences in false memory.

Response latencies for false memories: gist-based processes in normal aging

Three experiments have demonstrated that age-related increases in both probability and speed of false recognitions for word lists depended on the use of a gist-based memory strategy. When test conditions promoted a gist strategy, both younger and older participants were as likely to falsely recognize a thematically associated lure as to correctly recognize a studied item, and both groups were equally fast in making these decisions. However, when test conditions deemphasized a gist-based strategy, older adults were more likely than younger adults, and faster, to falsely recognize both strong and weakly associated lures. These findings suggest an age-related increase in reliance on gist-based processing that may underlie age differences in false memory.

1H-NMR study of the structural influence of Y64 substitution in Desulfovibrio vulgaris Hildenborough cytochrome c553

Y64 has been replaced in cytochrome c553 from Desulfovibrio vulgaris Hildenborough by phenylalanine, leucine, valine, serine and alanine residues. An NMR study of structural variation induced in both oxidoreduction states of the molecule has been carried out by analysing observed chemical-shift variations. Dynamic changes were evidenced using NH exchange. We have observed that the substitution has a drastic effect on the stability of the molecule in the reduced state, although there is no effect on the reduction potential of the cytochrome. Y64-->F substitution induces particular effects on the NH exchange at the N-terminal, C-terminal and central alpha-helices and increases the stability of the oxidized molecule.

Achromatic visual backward masking of colored stimuli in type I diabetes

On a visual backward masking task using color stimuli with an achromatic patterned mask, we compared the masking performances of 3 Type I diabetics with those of 9 participants in a control group. Analysis indicated that the diabetics show a marked decrement in performance with blue stimuli and a lesser decrement with red stimuli. Suggestions for further theoretical and parametric studies are discussed.

The effect of ring currents on carbon chemical shifts in cytochromes

Calculations suggest that some carbon chemical shifts in proteins should have large ring current shifts (> 1 ppm). We present 13C, 15N and 1H assignments for cytochrome C2 from Rhodospirillum rubrum, compare these with shifts for other cytochromes c, and show that the calculated ring current shifts are similar to experimentally observed shifts, but that there remain substantial conformation-dependent shifts of side-chain carbons. Ring current shifts as large as 6 ppm are observed. We show that the ring current effects do not seriously affect the Chemical Shift Index method for delineating secondary structure, but may have an impact on more precise methods for generating structural constraints.

New conformational properties induced by the replacement of Tyr-64 in Desulfovibrio vulgaris Hildenborough ferricytochrome c553 using isotopic exchanges monitored by mass spectrometry

In order to study the conformational stability induced by the replacement of Tyr-64 in Desulfovibrio vulgaris Hildenborough (DvH) cytochrome c553, fast peptic digestion of deuterated protein followed by separation and measurement of related peptides using liquid chromatography coupled to electrospray ionization mass spectrometry was performed. We show that the H-bonding and/or solvent accessibility properties were modified by the single-site mutation. The mutant proteins can be classified into two groups: the Y64F and Y64L mutants with nearly unchanged deuterium incorporation compared to the wild-type protein and the Y64S, Y64V and Y64A mutants with increased deuterium incorporation. The 70-74 peptide was the most affected by mutation of Tyr-64, the phenylalanine mutant inducing slight stabilization whereas the serine mutant was significantly destabilized. In addition, from the analysis of the overlapping 37-57 and 38-57 peptides we can conclude that the amide proton of Tyr-38 has been replaced by deuterium in all proteins.

Investigation of oxidation state-dependent conformational changes in Desulfovibrio vulgaris Hildenborough cytochrome c553 by two-dimensional H-NMR spectra

Two-dimensional nuclear magnetic resonance spectroscopy (2D-NMR) was used to assign the proton resonances of ferricytochrome C553 from Desulfovibrio vulgaris Hildenborough. The spin systems of 76 out of 79 amino acids were identified by J-correlation spectroscopy (COSY and HOHAHA) in H20 and D20 and correlated by nuclear Overhauser effect spectroscopy (NOESY). The proton chemical shifts are compared in both oxidized and reduced states of the protein at 23 degrees C and pH 5.9. Chemical shift variations between reduced and oxidized states are due to the paramagnetic contribution. Medium and long-range nOe demonstrate the lack of major changes between the two redox states. NMR data provide evidence that in this low oxidoreduction potential cytochrome, the oxidized state is more rigid than the reduced state.

Phototoxicity of some bromine-substituted rhodamine dyes: synthesis, photophysical properties and application as photosensitizers

The synthesis of some bromine-substituted rhodamine derivatives viz., 4,5-dibromorhodamine methyl ester (dye 2) and 4,5-dibromorhodamine n-butyl ester (dye 3) are reported. These dyes were synthesized to promote a more efficient cancer cell photosensitizer for potential use in in vitro bone marrow purging in preparation for autologous bone marrow transplantation. Spectroscopic and photophysical characterization of these dyes together with rhodamine 123 (dye 1) are reported in water, methanol, ethanol and also in a microheterogeneous system, sodium dodecyl sulfate. The possible mechanism of photosensitization is characterized in terms of singlet oxygen efficiency of these dyes. Singlet oxygen quantum yields for bromine-substituted dyes are in the range of 0.3-0.5 depending on the solvent. For dye 1 no singlet oxygen production is found. The photodynamic actions of these dyes in different cell lines are tested. It was found that dye 2 and dye 3 are efficient photosensitizers and mediate eradication of K562, EM2, myeloid cell lines (CML) and the SMF-AI rhabdomyosarcoma line.

Study of the new stability properties induced by amino acid replacement of tyrosine 64 in cytochrome C553 from Desulfovibrio vulgaris Hildenborough using electrospray ionization mass spectrometry

Hydrogen/deuterium exchange as well as charge state distribution monitored by electrospray ionization mass spectrometry were demonstrated to be a powerful and effective new tool for probing conformational properties of proteins in solution. In this paper, the influence of single amino acid replacements on the global conformation of cytochrome C553 from Desulfovibrio vulgaris Hildenborough using isotopic exchange monitored by electrospray ionization mass spectrometry is reported. Based on their respective charge state distributions and isotopic exchanges, we have differentiated relative stability of mutants and a ladder classification with the order being wild-type > Y64F = Y64L > Y64V > Y64A, under specific conditions of pH, is proposed.

Steady state and time-resolved fluorescence properties of metastatic and non-metastatic malignant cells from different species

Steady state and time-resolved fluorescence spectroscopy were employed to study the fluorescence from non-metastatic, metastatic and non-tumorigenic cell lines from different species. Excitations at 310 nm and 350 nm were used to monitor tryptophan and reduced nicotinamide adenine dinucleotide (NADH) fluorescence respectively. Subtle and consistent differences were observed between different categories of cell lines. It was found that the tryptophan to NADH fluorescence intensity ratio is higher in metastatic cell lines than in non-metastatic and normal cell lines. The fluorescence decay of the tryptophan residue in different cell lines was best described by triple exponential kinetics, whereas the NADH fluorescence decay was best described by mainly double and, in some cases, triple exponential kinetics. The average fluorescence lifetimes for tryptophan were in the range 2.5-3.7 ns. The average lifetime of NADH was lower (by a factor of approximately three) in metastatic cells than in non-metastatic cells and this finding is consistent for cell lines from different origins (rat or human). Correcting the fluorescence intensity for the average fluorescence lifetime of each species and for the volume of each cell line, it was shown that the concentrations of tryptophan and NADH are consistently higher in malignant metastatic cancer cells than in non-metastatic cells.

Purification and characterization of the formate dehydrogenase from Desulfovibrio vulgaris Hildenborough

Formate dehydrogenase from Desulfovibrio vulgaris Hildenborough, a sulfate-reducing bacterium, has been isolated and characterized. The enzyme is composed of three subunits. A high molecular mass subunit (83,500 Da) is proposed to contain a molybdenum cofactor, a 27,000 Da subunit is found to be similar to the Fe-S subunit of the formate dehydrogenase from Escherichia coli and a low molecular mass subunit (14,000 Da) holds a c-type heme. The presence of heme c in formate dehydrogenase is reported for the first time and is correlated to the peculiar low oxidoreduction potential of the metabolism of these strictly anaerobic bacteria. In vitro measurements have shown that a monoheme cytochrome probably acts as a physiological partner of the enzyme in the periplasm.

Control of the redox potential in c-type cytochromes: importance of the entropic contribution

The enthalpic and entropic components of the redox free energy variation of cytochrome c553 from Desulfovibrio vulgaris Hildenborough and its mutant Y64V, flavocytochrome b2 from Saccharomyces cerevisiae, and the different hemes of cytochromes c3 from Desulfovibrio vulgaris Miyazaki and Desulfovibrio desulfuricans Norway have been determined in 0.1 M Tris-HCl pH 7.0 (7.6 for cytochromes c3) at 25 degrees C by using nonisothermal potentiometric titrations. The set of available experimental data demonstrates that the entropic component plays an important role in the control of the redox potential in c-type and b-type cytochromes. The variation of the entropic component within the class of cytochromes characterized by a positive value of E degrees ' is proposed to be mainly determined by the variation of the exposure of the heme propionates to the solvent. In the case of tetraheme cytochromes c3, the thermodynamic characteristics vary largely among the hemes belonging to the same molecule, which reflects the environmental peculiarities of each heme and also the heme-heme redox interactions. This study substantiates the existence of compensatory effects between large and opposite contributions to E degree ' predicted by all the current theoretical models which are based on electrostatic free energy calculations.

Effects of the Tyr64 substitution on the stability of cytochrome c553, a low oxidoreduction-potential cytochrome from Desulfovibrio vulgaris Hildenborough

Cytochrome c553 from sulfate-reducing bacteria is a low-oxidoreduction-potential cytochrome. The primary and tertiary structures show notable differences when compared to mitochondrial cytochromes. Tyr64 replacement in cytochrome c553 provides evidence that this residue is not directly involved in the potential modulation but is mostly implicated in the hydrogen-bond network around the heme. While the different variants obtained did not induce drastic structural modifications, they did affect the stability of the protein. This decrease of stability in acidic and alkaline environments was observed by variations in the optical spectra and by mass spectrometry. In addition, the mobility of aromatic side-chain was found to be increased in the mutant proteins as monitored by two-dimensional NMR spectroscopy.

N-Phosphonomethyl dipeptides and their phosphonate prodrugs, a new generation of neutral endopeptidase (NEP, EC 3.4.24.11) inhibitors

Inhibitors of the zinc protease neutral endopeptidase (NEP, EC 3.4.24.11) offer significant therapeutic interest as antihypertensives due to their ability to potentiate the biological action of the circulating natriuretic hormone ANF (atrial natriuretic factor). N-Phosphonomethyl dipeptides bearing a central (4-phenyl)phenylalanine residue have been designed to exert potent and selective NEP inhibition. In particular, (S)-3-[N-[2- [(phosphonomethyl)amino]-3-(4-biphenylyl)propionyl]amino]propionic acid (10a) (CGS 24592) displayed high inhibitory potency in vitro (IC50 = 1.9 +/- 0.1 nM) and a long plasma half-life in rats but lacked oral bioavailability. This drawback was overcome by using esterase-sensitive (acyloxy)alkyl phosphonates. More remarkable, several diaryl phosphonate derivatives of 10a also performed as effective prodrugs. Specifically, the structurally simple diphenyl phosphonate 18 (CGS 25462) induced potent inhibition of NEP ex vivo for at least 8 h after oral administration to rats (30 mg/kg). Its antihypertensive effect was demonstrated in DOCA-salt rats. At 30 mg/kg orally, 18 caused a significant reduction in mean arterial pressure measuring -35 +/- 7 mmHg at 5-h postdosing. The alpha-aminomethyl phosphonate 18 represents a new generation of selective NEP inhibitors that combine high potency, long duration of action, and oral bioavailability. Therefore, it holds promise as a novel therapeutic agent for the treatment of human hypertension and congestive heart failure.

{The perception of mental health professionals of barriers to the delivery of mental health services for the aged in New Brunswick}

The present survey examines the barriers associated with the delivery of mental health services to the elderly as perceived by mental health professionals. The sample consisted of 139 professionals of the New Brunswick Mental Health Commission. The results reveal that the mean percentage of elderly clients in the practice of mental health professionals is low. The percentage of elderly clients in the practice of mental health professionals was positively correlated with training in gerontology. The attitudes of the respondents toward the elderly were either positive or neutral rather than negative. In addition, the results show that the barriers perceived by the professionals to explain the low utilization rates differ in order of importance from those acknowledged by the elderly. The lack of human resources was identified as the major barrier to the development of specific consultation services to the elderly. Finally, the implications of these results for the development of mental health consultation services for the elderly are examined.

The protein moiety modulates the redox potential in cytochromes c

Cytochrome c is one of the most thoroughly documented oxidoreduction proteins. Its electron transfer activity, which involves an association between the heme group and the polypeptidic chain, is correlated with the redox potential value of the heme group. The redox potential covers a wide range up to 0.8 V, an extreme case being observed in the low-potential cytochromes c from sulfate reducing bacteria. On of the main roles of the polypeptidic moiety consists of modulating the redox potential value of the heme group. In this paper, some structural factors that seem likely to be involved in maintaining the redox potential value are described.

Overexpression of Desulfovibrio vulgaris Hildenborough cytochrome c553 in Desulfovibrio desulfuricans G200. Evidence of conformational heterogeneity in the oxidized protein by NMR

Plasmid pRC41, containing the cyf gene encoding cytochrome c533 from Desulfovibrio vulgaris Hildenborough, was transferred by conjugation from Escherichia coli to Desulfovibrio desulfuricans G200. The structural properties of the purified protein were studied by one-dimensional and two-dimensional NMR. A heterogeneity in the folding of the cytochrome isolated from D. vulgaris Hildenborough and from D. desulfuricans G200 was observed for the oxidized from. Temperature, pH and salt-dependence studies indicated that the heterogeneity does not result from an intermediate in the protein unfolding process, but derives from two conformations which are not in dynamic equilibrium.

Intramolecular electron transfer in ferredoxin II from Desulfovibrio desulfuricans Norway

In order to elucidate the role of the two (4Fe-4S) clusters in ferredoxins and to determine whether an electron-transfer mechanism may occur between the clusters, the in vitro reduction of cytochrome c3 and cytochrome c553 by Desulfovibrio desulfuricans Norway ferredoxin II was studied using spectrophotometric techniques. Ferredoxin II, covalently cross-linked with either cytochrome c3 or c553, is an obligate intermediate in cytochrome reduction by pyruvate dehydrogenase. Both titration of the complex formation under 1H-NMR spectroscopy and cross-linking experiments between ferredoxin II and either cytochrome c3 or cytochrome c553 gave a stoichiometric ratio of 1:1. Modelling the protein yielded differences between the charge distributions around the two (Fe-S) clusters. The fact that Cluster 2 is blocked in the electron-transfer domain facing the cytochrome interacting heme, indicates Cluster 1 receives electron from pyruvate dehydrogenase. Consecutively, cytochrome reduction occurs owing to an intramolecular electron exchange between the two clusters of the ferredoxin. The properties of two (Fe-S) cluster ferredoxins are compared to those of monocluster ferredoxins and discussed in evolutionary terms.

Characterization of a lysine-to-glutamic acid mutation in a conservative sequence of farnesyl diphosphate synthase from Saccharomyces cerevisiae

The mutant gene erg20-2 was isolated from a yeast strain defective in farnesyl diphosphate synthase (FPPS). This strain had the unusual property of excreting prenyl alcohols such as geraniol. The nucleotide (nt) sequence, compared with that of the wild-type gene, showed a single nt change, resulting in a Lys197-->Glu substitution in FPPS which is directly involved in terpenic alcohol formation. In addition, disruption of ERG20 revealed that in yeast no other prenyl transferase is able to synthesize the FPP molecules required for essential non-sterol metabolites.

Backward visual masking in children and adolescents: sensory transmission, accrual rate and asymptotic performance

We have applied the Lagged Accrual Model of visual backward masking to a group of children (aged 10) and a group of adolescents (aged 15). The two groups did not differ on sensory transmission time, indicating that the speed of sensory transmission has already attained its maximum by age 10. The older group showed a significantly greater rate of information accrual and a greater amount of information extraction. An application of the model to previously published data revealed that very young children (aged 5) have slower sensory transmission times.

Sterol pathway in yeast. Identification and properties of mutant strains defective in mevalonate diphosphate decarboxylase and farnesyl diphosphate synthetase

Yeast mutant strains auxotrophic for ergosterol and blocked in mevalonate diphosphate decarboxylase (erg19) and farnesyl diphosphate (FPP) synthetase (erg20) were isolated. The main feature of the mutants blocked in FPP synthetase is their ability to excrete prenyl alcohols, such as geraniol and farnesol. The isolation of the functional ERG20 gene allowed us to show that farnesyl diphosphate synthetase could be a rate limiting enzyme in ergosterol biosynthesis in yeast.

4-(Phosphonoalkyl)- and 4-(phosphonoalkenyl)-2-piperidinecarboxylic acids: synthesis, activity at N-methyl-D-aspartic acid receptors, and anticonvulsant activity

A series of 4-(phosphonoalkyl)- and 4-(phosphonoalkenyl)-2-piperidinecarboxylic acids were synthesized, and their biological activity was assessed as competitive ligands for the NMDA receptor, both in vitro by using a receptor binding assay ([3H]CGS 19755 binding) and in vivo by using an NMDA seizure model in mice. The analogues were also evaluated in [3H]AMPA and [3H]kainate binding to assess their affinity for non-NMDA excitatory amino acid receptor subtypes. A number of these analogues show potent and selective NMDA antagonistic activity both in vitro and in vivo. Most notable are 4-(phosphonomethyl)-2-piperidinecarboxylic acid (1a) (CGS 19755) and the phosphonopropenyl analogue 1i, both of which show anticonvulsant activity in the 1-2 mg/kg ip range. With the aid of computer-assisted modeling, a putative bioactive conformation for AP-5 is hypothesized from the SAR data presented and a preliminary model for the antagonist-preferring state of the NMDA receptor is presented.

Ontogeny of receptors for thyrotropin-releasing hormone in the rat brain

Developmental changes in the thyrotropin-releasing hormone (TRH) receptor concentrations of hypothalamic and certain extrahypothalamic structures in the rat were evaluated from 2 days after birth until sexual maturity. The maturational pattern of TRH receptors in hypothalamus, striatum and amygdala follow that of the pituitary and all show the same kinetic properties. The developmental pattern also coincides with that of other components of the hypothalamic-pituitary-thyroid axis. In all tissues, the concentration of receptors increased in early life to reach a maximum between 10 and 30 days of age and then decreased gradually to adult values. Development of TRH receptors reflected changes in the number of receptor sites but not in binding affinity, which remained constant and suggests that the TRH receptor is identical in all 4 tissues studied. These results indicate the parallel development of pituitary and central nervous system TRH receptors.

Modulation of rat pancreatic amylase secretion and muscarinic receptor populations by chronic bethanechol treatment

F8P6effect of a chronic bethanechol treatment (12 mg X kg-1 X day-1 i.p., for 14 days) was investigated on pancreatic amylase secretion and muscarinic cholinergic receptors in the rat. Dispersed pancreatic acini were used to evaluate enzyme secretion and binding of [3H]N-methylscopolamine, [( 3H]NMS). The bethanechol treatment caused a 4 fold decrease in sensitivity of the pancreas for amylase release in the presence of carbamylcholine, the EC50 being shifted from 0.69 microM to 2.9 microM. Receptor concentration was reduced by 42%, from 3360 to 1930 fmol/mg DNA. The equilibrium dissociation constant (KD) of the receptors for the ligand remained unchanged at 0.17 nM. Binding analysis of carbachol on the muscarinic receptors in terms of two classes of binding sites indicated that the shift in the dose-response curve of amylase secretion was accompanied by modifications to the high and low affinity forms. The maximal number of high affinity sites remained the same while their affinity was greatly decreased from 0.24 to 6.1 microM. The low affinity form showed a moderate decrease in affinity from 34 to 150 microM but a large drop in their numbers from 2620 to 890 fmol/mg DNA. These results suggest that the shift in the amylase dose-response curve to carbamylcholine, noted following bethanechol treatment in vivo, could be coupled with the observed change in affinity of the two agonist forms of muscarinic receptor in the pancreas. However, gradual occupancy or formation of the high affinity form of muscarinic receptors by cholinergic agonist corresponds well with the gradual stimulation of amylase release.

Linear eccrine nevus with comedones

We report herein a case of a linear nevus comedonicus associated with tumors of sweat gland origin. We propose the term "linear eccrine nevus with comedones" as a suitable title for this disorder. Several similar cases in the literature are reviewed.

Microscopically controlled surgery for extramammary Paget's disease

In five cases of extramammary Paget's disease (EMPD), the neoplasms were removed under complete microscopical control by means of fixed-tissue chemosurgical technique in one case and fresh-tissue technique in four cases. In each lesion there were histologically involved areas extending several centimeters into clinically normal-appearing skin. All patients have been free of the disease for periods from four months to nine years. Other authors using conventional surgery have reported a recurrence rate of 44%. Microscopically controlled surgery offers the most reliable method of removing all of the neoplastic tissue EMPD and preserves as much normal tissue as possible.